The present application is a continuation of International Application PCT/SE2004/000269, filed Feb. 26, 2004, which claims priority to Swedish Application No. 0300594-9, filed Mar. 5, 2003.
The present invention relates to a device for driving a wheel of a vehicle, which device comprises a hub for carrying a wheel in a rotationally fixed manner, a planetary gear connected between a driving axle and the hub, which planetary gear comprises a planet carrier which is connected in a rotationally fixed manner to the hub, and an arrangement for fixing the hub and the planet carrier in the intended position relative to one another in the axial direction. In particular, the device is intended to be applied in a work vehicle, such as a wheel loader, dumper or the like. However, the invention could also be utilized in other heavy duty vehicles, such as trucks and buses.
By virtue of arranging a planetary gear at each driving wheel in this way, a reduction in the rotational speed from the driving axle to the hub and an increase in torque from the driving axle to the hub are brought about.
WO99/03699 describes a planetary transmission for a vehicle. The hub comprises a journal extending in the axial direction which is arranged in a hole in the planet carrier. The hole has internal splines, and the journal has external splines for bringing about rotational locking in relation to one another. A plate with a greater radial extent than the journal is arranged axially inside the planet carrier and is connected to the hub via a number of screws through holes in the plate and the journal of the hub. In this way, it is ensured that the hub is axially fixed relative to the planet carrier. When the hub rotates, these screws are subjected to a relatively great varying load and tend to suffer fatigue and to break off after a period of operation.
It is desirable to produce a device for driving a vehicle wheel which leads to longer life and in particular provides a stronger construction as far as fatigue resistance is concerned.
According to an aspect of the present invention, both the hub and the planet carrier comprise a hole which extends in the axial direction, at least one of the holes forms at least a part of a continuous opening through the hub and the planet carrier in the axial direction, and the fixing arrangement comprises an elongate element arranged in the continuous opening and means for fixing the hub and the planet carrier relative to one another in the axial direction via the elongate element.
According to an aspect of the invention, the holes in the hub and the planet carrier extend centrally around the intended line of rotation of the hub. This results in a construction which is strengthened further with regard to fatigue resistance.
The elongate element is thus not subjected to a varying load when the hub rotates.
According to another aspect of the invention, the fixing arrangement comprises a portion with at least in part a greater extent in the radial direction than the holes in the hub and the planet carrier, and this portion is connected firmly to the elongate element so as to form a counterstay at a first end of the hole. The fixing arrangement also comprises interacting means for tightening the hub and the planet carrier, which tightening means are arranged at a second end of the holes in the hub and the planet carrier.
According to another aspect of the invention, the radially projecting portion comprises at least one first guide surface for guiding interaction with a correspondingly designed surface of the hub. In this way, the wear which can arise on a spline connection between the hub and the planet carrier when radial relative movement between these takes place is reduced. Furthermore, owing to this, the splines can be designed in a better way from the point of view of strength. Extra machining operations in the form of grinding spline tops on the hub axle are also avoided.